Help with VLOOKUP

I'm looking for some help using VLOOKUP or another formula that might be able to accomplish what I need to have done.

Cell D2 is any whole number between 75000 - 2,000,000

Column S is a list of whole numbers from 75000 up, which counts in 5000 increments.
Column T is a corresponding factor to Column S. For example:

75000

0.825

80000

0.850

85000

0.885

90000

0.921

95000

0.959

100000

1.000

And so on.

Currently I'm using a basic VLOOKUP formula, =VLOOKUP(D2,S2:T115,2), however, this of course only allows the user to enter a number the exactly corresponds to a value in column S.
What I need to do is develop the numbers in between each value in column S&T so that a user may enter any number (in increments of 100) in Cell D2 and get a correct factor.

So basically if the user enters 82500 in cell D2 Excel needs to recognize that cells S2 & S3 are the cells in play, reference each of the factors in column T (.825 & .885), find the difference (.35), divide by 50 (.007) and then multiply by ((82500-S2)/100))=.175+T2

Is there a way I can work that into a formula in Excel?
Any assistance would be greatly appreciated!